(19)
(11) EP 0 640 489 A2

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication:
01.03.1995 Bulletin 1995/09

(21) Application number: 93115189.8

(22) Date of filing: 21.09.1993
(51) International Patent Classification (IPC)6B41J 5/10
(84) Designated Contracting States:
DE GB

(30) Priority: 16.08.1993 US 106597

(71) Applicants:
  • Chiu, Wilson L.
    Yorba Linda, California 92686 (US)
  • Lam, Hau Chung
    Kowloon (HK)

(72) Inventors:
  • Chiu, Wilson L.
    Yorba Linda, California 92686 (US)
  • Lam, Hau Chung
    Kowloon (HK)

(74) Representative: Baillie, Iain Cameron et al
c/o Ladas & Parry Altheimer Eck 2
80331 München
80331 München (DE)


(56) References cited: : 
   
       


    (54) Foldable keyboard


    (57) A folding keyboard for a miniature computer or other data processing device which permits a standard key spacing to be retained while enabling folding of the keyboard to reduce its overall size for storage or carrying purposes. In another aspect, the thickness of the keyboard when in folded position is reduced in some embodiments by maintaining its keys in depressed positions.




    Description

    BACKGROUND OF THE INVENTION


    Field of the Invention



    [0001] This invention relates to keyboards and has particular reference to keyboards associated with data processing equipment such as computers, typewriters, etc.

    Description of the Prior Art



    [0002] The miniaturization of electronic computers, etc., has brought about the desire for corresponding miniaturization of keyboards associated with such equipment. However, the limiting factor in the reduction in size of keyboards is the spacing and size of the keys since the minimum key spacing is dictated by the size of an average operator's fingers.

    SUMMARY OF THE INVENTION



    [0003] Therefore, the present invention may provide a keyboard which is collapsible into a small space, yet will retain a normal key spacing. The folding of the keyboard may be permitted regardless of the type or pattern of its keys. Further, the thickness of a folding keyboard when in folded condition may be minimized.

    [0004] The invention may further protect and hide adjacent ends of adjacent units of a folding keyboard when it is in folded condition and provide a keyboard of simple and inexpensive construction.

    [0005] According to an aspect of the invention, the keyboard may be divided into two units arranged side by side. The adjoining boundaries of the units may be formed to present an unbroken pattern of adjacent keys when the keyboard is unfolded. Thus, in a keyboard in which the key rows are located in the "QWERTY" format found on most computers and typewriters, wherein keys in one row are staggered relative to the keys in an adjoining row, the boundaries of the units follow complementary jagged lines extending between adjacent keys near the center of the keyboard. However, the boundaries of keyboard units of keyboards arranged in different patterns would follow different complementary lines.

    [0006] One of the keyboard units is pivotally supported to swing about an axis located above the plane of the key tops and in substantial vertical alignment with the boundary lines of the adjoining unit to enable one unit to be swung 180° into a folded position relative to the other without interference.

    [0007] The keyboard units are of substantially equal width and preferably of a width substantially equal to the width of a computing device to which one of the units is preferably integrally attached.

    [0008] In certain modified forms of the invention, links are provided to pivotally connect the separate keyboard units, enabling one to be swung 180° into overlapping position relative to the other.

    [0009] In a further modification, a flexible cover is provided. When the moveable keyboard unit is swung into folded position, the cover is extended over the now separated jagged boundary edges of both units to protect the same and to present a pleasing appearance to the whole.

    [0010] In another modification, the keys are moved to depressed positions when folding is to occur to result in a relatively thin compact keyboard assembly. When the moveable keyboard unit is subsequently swung to unfolded position, the keys may be returned to undepressed positions.

    [0011] In yet another modification, an end cover member is pivotally connected to the keyboard units to cover the exposed ends of the units when they are in folded condition and side cover elements are carried by the end cover members and are slidable along the units to further cover the exposed ends of the units.

    [0012] In a further modification, a pair of end cover members are pivotally connected together and to the two keyboard units in a manner to extend across and cover the exposed ends of the units when in folded condition.

    [0013] In a still further modification, the keyboard is split along a pivotal axis extending parallel to the lengths of the various row of keys.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0014] The manner in which the above and other objects of the invention are accomplished will be readily understood on reference to the following specification when read in conjunction with the accompanying drawings, wherein:

    FIG. 1 is a plan view of a keyboard embodying the present invention associated with a computing device, the keyboard being shown in unfolded operating condition.

    FIG. 2 is a front elevational view of the keyboard, partly in section.

    FIG. 3 is a fragmentary elevational view of a modified form of a swingable connection between the keyboard units.

    FIG. 4 is a fragmentary view similar to FIG. 3 but showing the moveable keyboard unit in folded condition.

    FIG. 5 is a fragmentary elevational view of another modified form of swingable connection between the keyboard units.

    FIG. 6 is a view similar to FIG. 5 but showing the moveable keyboard unit in folded condition.

    FIG. 7 is a top plan view, partly broken away, of a modified form of the invention, illustrating the same in unfolded condition and showing a flexible cover strip for covering the ends of its separate keyboard units when they are moved to a folded condition.

    FIG. 8 is a view similar to FIG. 7 but illustrating the keyboard units in folded condition.

    FIG. 9 is a front elevational view, partly broken away, of the keyboard arrangement of FIG. 7 showing the same in an unfolded condition.

    FIG. 10 is a front elevational view similar to FIG. 9 but illustrating the keyboard in a folded condition.

    FIG. 11 is a sectional elevational view of a modified form of the invention, illustrating means for holding the keys in depressed positions to enable folding of the keyboard into a relatively thin compact package.

    FIG. 12 is a view similar to FIG. 9 but showing one of the keys in depressed position.

    FIG. 13 is a front elevational view, partly broken away, of a modified form of the invention, showing the keyboard units in folded condition.

    FIG. 14 is a view similar to FIG. 13 but showing the keyboard units in unfolded condition.

    FIG. 15 is a top plan view, partly broken away, of the modification shown in FIG. 13 and 14 in unfolded condition.

    FIG. 16 is a front elevational view, partly broken away, of another modified form of the invention, showing the keyboard units in folded condition.

    FIG. 17 is a view similar to FIG. 16 but showing one of the keyboard units in partly unfolded condition.

    FIG. 18 is a view similar to FIG. 16 and 17 but showing the keyboard units in unfolded condition.

    FIG. 19 is a fragmentary transverse sectional view taken along line 19-19 of FIG. 18.

    FIG. 20 is a plan view of another modified form of the invention showing the separate keyboard units foldable about an axis extending parallel to the lengths of the key rows.

    FIG. 21 is a side view of the keyboard of FIG. 20.


    DESCRIPTION OF THE EMBODIMENT SHOWN IN FIG. 1 AND 2



    [0015] The keyboard, generally indicated at 11, is comprised of a plurality of depressible data entry keys 12 arranged in rows 13 according to the "QWERTY" format wherein the keys of one row are staggered relative to the keys in other rows.

    [0016] The keyboard 11 is shown as integrally associated with a miniature computing or other data processing device generally indicated at 14, and function keys 15 are provided in addition to the data entry keys 12 to control the computing device.

    [0017] As seen in FIG. 2, the keys 12 and 15 have key tops 16 normally extending in a common plane, each key including a key stem 17 slidably mounted in a bearing 18 formed in a key plate 20. Each key is normally held in its illustrated raised position by an elastomeric spring member 21 which rests on a bottom key plate 22 preferably formed of electrically insulated material. Upon depression of a key, the member 21 will yield and a contact 23 carried thereby will bridge two or more stationary contacts 24 on the plate to complete a suitable circuit (not shown) leading to an appropriate circuit in the computing device 14.

    [0018] It will be noted that the keyboard is divided into two similar units generally indicated at 25 and 26.

    [0019] The right-hand keyboard unit 25 comprises the aforementioned key plates 20 and 22 held in spaced relation by front, side and rear walls 27, 28 and 29, respectively. The left-hand keyboard unit 26 similarly comprises a key top plate 30, a bottom key plate 31 and front, side and rear walls 32, 33 and 34, respectively.

    [0020] The front walls 27 and 32 have upstanding lugs 35 which are connected by a pivot pin 36 and the rear walls 29 and 34 are likewise provided with lugs 37 connected by a pivot pin 38. The pins 37 and 38 are aligned with each other to form a folding axis 40 located slightly above and parallel to the plane of the key tops 16.

    [0021] The key plates 20 and 30 of the two keyboard units are formed along complementary jagged edges 41 and 42 which extend between adjacent keys 12 and 15 in the central part of the keyboard. Parts of such edges are either vertically aligned with the folding axis 40 or are close thereto.

    [0022] It will be noted that the keyboard units 25 and 26 are of similar width and at least substantially equal to the width of the computing device 14. The unit 26 is integrally attached to the device 14 in a manner not shown. Thus, when the right-hand unit 25 is swung about axis 40 into its folded condition shown by dot-dash lines 25' the width of the keyboard will substantially equal the width of the computing device but when the unit 25 is swung to its unfolded position of FIG. 1 it will be a normal size keyboard.

    KEYBOARD OF MODIFIED EMBODIMENT SHOWN IN FIG. 3 AND 4



    [0023] FIG. 3 and 4 illustrate a modified form of pivotal connection between right- and left-hand keyboard units 125 and 126. A link 45 is pivoted at 46 to the front wall 127 of keyboard unit 125. A roller 47 carried by link 45 engages a relatively wide slot 48 formed in the front wall 132 of the left-hand keyboard unit 126. A similar linkage connection (not shown) is provided between the rear walls of the keyboard units.

    [0024] The roller 47 normally rests in a detent pocket formed in the slot 48 by a shoulder 49. By pulling the keyboard unit 125 to the right, the roller 47 is moved to the right-hand end of the slot 48 into a detent pocket also formed by shoulder 49, as shown in FIG. 4, enabling the unit 125 to be swung about pin 46 into its folded position of FIG. 4.

    DESCRIPTION OF MODIFIED EMBODIMENT SHOWN IN FIG. 5 AND 6



    [0025] FIG. 5 and 6 show another modified form of swingable connection between right- and left-hand keyboard units 125A and 126A. A pair of levers or bell cranks 75 and 76 are pivoted together at 77 on one side of the keyboard. Bell crank 75 is pivoted to unit 126A at 78 and has a pin 80 slidable along slot 81 in unit 125A. Likewise, bell crank 76 is pivoted at 82 to unit 125A and has a pin 83 slidable along slot 88 in unit 126A.

    [0026] Normally, when in unfolded position shown in FIG. 5, the unit 125A abuts unit 126A to maintain the keys (not shown) carried thereby in a common plane. However, by swinging the unit 125A upward the bell cranks 75 and 76 will guide the same into a folded position relative to the unit 126A as shown in FIG. 6.

    [0027] A similar swingable connection is provided on the opposite side of the keyboard.

    [0028] Thus, it will be seen that the pivotal connections comprising bell cranks 75 and 76 will be effective to guide the keyboard unit 125A into overlapping or folded position relative to unit 126A but will be located below the level of such units when they are in their unfolded operating condition of FIG. 5 and will therefore not interfere with an operator depressing the different keys.

    DESCRIPTION OF MODIFIED EMBODIMENT SHOWN IN FIG. 7 TO 10



    [0029] FIG. 7 to 10 illustrate a modified form of the invention in which the keyboard is separated into right- and left-hand units generally indicated at 225 and 226 along complementary jagged edges 241 and 242, similar to jagged edges 41 and 42 of FIG. 1 and 2.

    [0030] The front and rear keyboard walls 227 and 229 of the unit 225 are connected to the corresponding walls 232 and 234 of the unit 226 by aligned pivot pins 237 and 238 to permit folding of the unit 225 into its folded position shown in FIG. 8 and 10.

    [0031] The walls 232 and 234 of unit 226 have arcuate extensions 50 extending concentrically about the pivot pins 237 and 238. Inwardly facing arcuate grooves 51 are formed in the wall extensions 50 and along the walls 232 and 234 to slidably receive a thin flexible cover strip 52 of plastic, cloth or the like. The latter is suitably secured at 53 to one end of the bottom wall 222 of the right-hand keyboard unit 225. The cover strip 52 extends over arcuate portions of extensions 49 of the front and rear walls, 227 and 229, and tension spring 54 and 55 are connected between the opposite end of the cover strip 52 and a suitable part of the keyboard unit 226 to maintain the cover strip in a taut condition. Thus, when the keyboard unit 225 is swung into its folded position of FIG. 8 and 10 the cover strip 52 will be drawn through the grooves 51 and over the arcuate portions 49 to protect the exposed and jagged edges 241 and 242 of the two keyboard units and to present a rounded pleasing appearance. When the unit 225 is swung to its unfolded position as shown in FIG. 7, the cover strip 52 will be drawn within the keyboard unit 226 where it is hidden from view.

    DESCRIPTION OF THE MODIFIED EMBODIMENT SHOWN IN FIG. 11 AND 12



    [0032] FIG. 11 and 12 illustrate a further embodiment in which the various keys of the right- and left-hand keyboard units 325 and 326 are moved to depressed positions pursuant to folding of the keyboard units so that the overall thickness of the keyboard may be reduced when in folded condition while allowing a normal key stroke when the keyboard is unfolded. For this purpose, each of the data entry and function keys, such as shown at 316, has a pin 60 extending from the stem 319 thereof and passing through a vertical slot 61 in the respective keyboard bearing 318. The various pins 60 of those keys in an aligned row also engage camming slots 62 formed in a slide bar 63 suitably supported in a manner not shown for endwise movement.

    [0033] A knob 64 is attached to slide bar 63 and extends through a slot 65 in the key top plate 320. When moving the slide bar 63 to the left from its FIG. 11 position, the camming slots 62 will cam all of the keys associated with slide bar 63 into fully depressed positions as seen in FIG. 12, thus reducing the thickness of the keyboard. A separate slide bar (not shown) similar to slide bar 63 is provided for each row of keys and suitable means (not shown) can be provided to move all such cam bars in unison.

    [0034] The foregoing arrangement enables the pivot or folding axis of the two keyboard units 325 and 326, as formed by aligned pivot pins 337, 338, to be located below the plane of the key tops 316 when in depressed positions, as shown in full lines in FIG. 11, resulting in a relatively thin, compact package when the keyboard is in folded condition.

    DESCRIPTION OF MODIFIED EMBODIMENT SHOWN IN FIG. 13 TO 15



    [0035] FIG. 13 to 15 illustrate another modified form of the invention in which right- and left-hand keyboard units, 425 and 426, similar to units 25 and 26 in FIG. 1, are provided.

    [0036] The front wall 427 of unit 425 is pivotally connected to the front wall 432 of the unit 426 by a pivot pin 90. Likewise, the rear walls (not shown) of the units are similarly pivotally connected by a pivot pin extending coaxial with pin 90 to enable swinging of the unit 425 between its folded position shown in FIG. 13 and its unfolded position shown in FIG. 14.

    [0037] It will be noted that the adjacent ends of the walls 427 and 432 overlap and the top key plates 420, 430 and bottom key plates 422, 431 terminate inwardly from the ends of these walls, as indicated at 91, to enable complete unfolding of the unit 425.

    [0038] For the purpose of covering and protecting the edges of the units 425 and 426 when in folded condition, an end cover member 92, preferably formed of a relatively rigid plastic material, such as polypropylene, is provided having end walls at opposite ends, one of which is shown at 93. The latter are pivotally supported by the aligned pivot pins 90 to swing independently of the keyboard units 425 and 426. The cover member 92 is reduced in thickness at 94 and 95 to form hinges for pivotally supporting side cover elements 96 and 97, respectively. The latter are slidable along the bottom key plates 422 and 431 of the respective keyboard units 425 and 426, and for this purpose, each cover element is formed with coaxial laterally extending studs 98, which are guided along slots 100 formed in the respective front and rear walls of units 425 and 426. Thus, as the keyboard unit 425 is swung into its folded condition of FIG. 13, the cover elements 96 and 97 will slide along the respective keyboard units 425 and 426 to cover the otherwise exposed ends of the units.

    DESCRIPTION OF MODIFIED EMBODIMENT OF FIG. 16 TO 19



    [0039] FIG. 16 to 19 illustrate another embodied form of the invention in which right- and left-hand keyboard units 525 and 526, similar to units 25 and 26, respectively, of FIG. 1 are provided.

    [0040] The unit 526 comprises a front wall 100 and a similar rear wall (not shown) joined by a bottom key plate 101. The latter unit is preferably formed of a relatively rigid plastic, such as polypropylene, and is integrally connected to an end cover member 102 by a section 103 of reduced thickness forming a hinge joint. Cover member 102, in turn, is connected through a second hinge joint 104 to a second end cover member 105.

    [0041] The right-hand keyboard unit 525 is pivotally connected to the left-hand unit 526 by a pivot pin 106 enabling it to be swung between its folded position depicted in FIG. 16 to its unfolded position of FIG. 18.

    [0042] The unit 525 is also provided with slots, one of which is shown at 108, in its front and rear walls which slidably embrace coaxial pins 109 extending from side walls 110, which extend from opposite sides of the cover member 105.

    [0043] In pivoting the keyboard unit 525 to its unfolded position of FIG. 18, the pin and slot connections 108, 109 cause the cover members 102 and 105 to rotate about their hinges 104 and 103 to assume the aligned position shown in FIG. 18. During this movement, the unit 525 fits between the side walls 110 on cover member 105 and similar side walls 111 on cover member 102.

    [0044] It will be noted that when the keyboard unit 525 is swung into its folded position of FIG. 16, the cover members 102 and 105 nest together against the adjacent ends of both keyboard units 525 and 526, thus covering the same to exclude entrance of dust and dirt and to present a pleasing appearance.

    DESCRIPTION OF MODIFIED EMBODIMENT SHOWN IN FIG. 20 AND 21



    [0045] FIG. 20 and 21 illustrate another embodiment employing a keyboard 611 similar to that shown in FIG. 1. However, the keyboard is divided into two units 625 and 626 having mating edge walls 120 and 121, respectively, which extend between and parallel to two of the rows of keys 612 and 615.

    [0046] Coaxially aligned pins 122 and 123 pivotally connect side walls 124, 125 of keyboard unit 625 to side walls 126, 127 of unit 626. Such pins are located slightly above the tops of the keys 612 and 615 enabling the unit 626 to be swung between its unfolded position shown in full lines in FIG. 21 and its folded position shown in dot-dash lines 626a.

    [0047] In the various aforementioned embodiments, it is assumed that the immovable keybaord unit of each is integrally connected to a computer or like device as indicated at 14 in FIG. 1 and at 614 in FIG. 20. However, as another aspect of the invention, the keyboard unit in such embodiments could be physically separated from the device 14 or 614 and the various keys could be remotely connected to the device or to any other device through flexible wire circuits or the like.

    [0048] It will be seen from the foregoing that we have provided a novel keyboard structure which enables the keys to be spaced apart the normal spacing to permit unhindered operation by an operator's fingers while presenting a small compact package when folded. Although the folding keyboard of this invention has special utility for use on miniaturized computers or the like, it will be apparent that it has applicability for use on computers of larger size as well.


    Claims

    1. Keyboard means comprising:
       a first keyboard unit carrying a first plurality of touch responsive keys,
       a second keyboard unit carrying a second plurality of touch responsive keys, and
       pivotal supporting means supporting said second keyboard unit for movement from an operating position to a folded storing position.
     
    2. Keyboard means as defined in claim 1 wherein the pivotal supporting means comprises:
       first pivot means positioned at one side of the pluralities of keys pivotally connecting the keyboard units, and
       second pivot means positioned at the opposite side of said pluralities of keys pivotally connecting said keyboard units,
       the pivot axes of the first and second pivot means being coaxial.
     
    3. Keyboard means as defined in claims 1 or 2 including a data processing unit integral with said first keyboard unit, said first keyboard unit having a width substantially equal to the width of said data processing unit, and said second keyboard unit having a width substantially equal to the width of said first keyboard unit.
     
    4. Keyboard means as defined in claim 2 wherein said supporting means comprises a link pivotally connected at one end to said first keyboard unit and pivotally connected at the opposite end to said second keyboard unit whereby said second keyboard unit can be folded over said first keyboard unit.
     
    5. Keyboard means as defined in claims 1 to 4 wherein said supporting means comprises:
       a pair of levers,
       pivotal means pivotally connecting said levers together,
       each of said levers being pivotally connected at one end to a respective one of said keyboard units and connected by a pin and slot arrangement to the other of said keyboard units,
       whereby one of the keyboard units can be moved from said operating position to said folded storing position.
     
    6. Keyboard means comprising:
       a first keyboard unit carrying a first plurality of touch responsive keys,
       a second keyboard unit carrying a second plurality of touch responsive keys,
       means supporting said second keyboard unit to permit its movement from a first position wherein one end thereof lies in abutting relationship with one end of said first keyboard unit to a second position wherein said second plurality of touch responsive keys is folded over said first plurality of touch responsive keys,
       a flexible cover member,
       first connecting means connecting one end of said flexible cover member to an end of one of the keyboard units, and
       second connecting means connecting the opposite end of said flexible cover member to the other of the keyboard units, whereby when said second keyboard unit is moved to said second position said flexible cover member is drawn over the otherwise exposed abutting ends of said keyboard units.
     
    7. Keyboard means as defined in claims 6 or 7 wherein the supporting means comprises pivot means.
     
    8. Keyboard means as defined in claim 7 wherein the second connecting means comprises spring tensioning means for maintaining said flexible cover member taut at all times.
     
    9. Keyboard means as defined in claim 8 including guide means for guiding said flexible cover member in a predetermined path upon movement of said second keyboard unit between its first and second positions.
     
    10. Keyboard means as defined in claim 9 wherein said guide means is effective to guide said flexible cover member in an arc concentric with the pivot axis of said pivot means.
     
    11. Keyboard means comprising:
       a first keyboard unit carrying a first plurality of depressible keys,
       a second keyboard unit carrying a second plurality of depressible keys,
       means supporting said second keyboard unit for movement from a first position wherein the tops of all of its depressible keys lie in a common plane, to a second position wherein said second plurality of depressible keys are folded over said first plurality of depressible keys,
       spring means for normally maintaining said depressible keys in raised position, and
       means for selectively moving said depressible keys into depressed positions.
     
    12. Keyboard means as defined in claim 11 wherein said means supporting said second keyboard unit comprises pivot means whose pivot axis lies below the plane of the depressible key tops when the depressible keys are in raised positions and lies above the plane of said depressible key tops when said depressible keys are in depressed positions.
     
    13. Keyboard means as defined in claim 12 wherein said means for selectively moving said depressible keys into depressed positions comprises camming means moveable from a first position to a second position for camming said keys into said depressed positions.
     
    14. Keyboard means as defined in claim 13 wherein said camming means comprises camming members moveable in a direction at right angles to the direction of movement of said depressible keys, and
       connecting means between said camming members and each of said depressible keys whereby movement of said camming members in the direction of movement thereof cams all of said depressible keys into depressed positions.
     
    15. Keyboard means as defined in claims 11 to 14 including a computing device integral with said first keyboard unit,
       said first keyboard unit having a width substantially equal to the width of said computing device, and
       said second keyboard unit having a width substantially equal to the width of said first keyboard unit.
     
    16. Keyboard means as defined in claim 1 wherein said pivotal supporting means pivotally connects said second keyboard unit to said first keyboard unit for movement from an operating position, wherein one end of said second keyboard unit lies adjacent one end of said first keyboard unit, to said folded storing position wherein said second keyboard unit is folded over said first keyboard unit, and which includes a cover member,
       said pivotal supporting means serving to support said cover member to extend across the previously adjacent ends of the keyboard units when said second keyboard unit is moved to its folded storing position.
     
    17. Keyboard means as defined in claim 1 wherein said pivotal supporting means pivotally connects said second keyboard unit to said first keyboard unit for movement from said operating position, wherein one end of said second unit lies adjacent one end of said first keyboard unit, to said folded storing position wherein said second keyboard unit is folded over said first keyboard unit, and which includes:
       a cover member,
       supporting means supporting said cover member to extend across the adjacent ends of the keyboard units when they are in said storing position, and
       side cover elements connected to said cover member, said side cover elements being pivotally moveable with respect to said keyboard units when said second keyboard unit is moved between said folded storing position and said operating position.
     
    18. Keyboard means as defined in claim 17 including means for guiding said cover member in sliding engagement with the first and second keyboard units.
     
    19. Keyboard means as defined in claim 1 wherein said pivotal supporting means includes:
       a first cover member pivotally connected to said first keyboard unit,
       a second cover member pivotally connected to said first cover member, and
       means pivotally connecting said second cover member to said second keyboard unit whereby when said second keyboard unit is in said folded storing position the first and second cover members will enclose adjacent ends of the keyboard units.
     
    20. Keyboard means as defined in claim 1 wherein said keys extend in parallel rows and said pivotal supporting means supports said second keyboard unit for movement around an axis parallel to the lengths of said parallel rows.
     




    Drawing